Many people thing about electronic voting only for presidential elections and so on, but where I think it could be a game changer is in bringing current democracies on the way to a system closer to what is known as direct democracy where implicated citizens could use their vote in very specific decisions and other people could delegate (temporally , with easy possibility of revocation and discretionally) to political parties or representatives so they could decide for them.
I envision a system with independent census and electoral entities and using smartcard chips with certificates. I just made it up very fast it still has very vague parts, maybe inconsistencies but I feel starting from here it could be a sound system.
The census entity is in charge of providing means to eligible citizens to sign their votes. For instance a smartcard with public private key, a protocol should be established in a way that the census entity knows which certificates has issued but cannot relate them to specific people.
When a poll is called independent parties can apply to become electoral entities for that specific poll, these can be public entities, NGO's, etc... a number of them is somehow certified and chosen.
During the time allowed to vote, each citizen signs his vote using his smartcard and sends it to all or a subgroup of the electoral entities chosen for the poll, independently of this, with his smartcard and any time during or even before the voting time he signs a request to the census entity stating his intention to vote.
At the end of the voting all voting logs are signed by each of the entities and made public, these logs have all the votes, signed with their respective certificates, they've received, also the census entity makes public a log with all the voting requests made.
The result of the election is not actually calculated by these entities but anyone can produce it by processing the logs, a protocol to work out inconsistencies should be designed, but it should be possible to work out given a honest census entity and the nature of public/private key certificates.